Within one month of the start of the study, patients will be requested to refrain from drinking grapefruit and orange juice. The study will take place in 1 sunitinib treatment cycle of 6 weeks (4 weeks of treatment with sunitinib (week 1-4) and 2 weeks off period (week 5 and 6). The grapefruit juice or orange juice will be administered 3 times per day for 1 period of 3 days in the 4th week of treatment with sunitinib.